The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of processing and manufacturing ICs and, for these advancements to be realized, similar developments in IC processing and manufacturing are needed.
For example, multi-gate devices have been introduced by increasing gate-channel coupling as an effort to improve gate control, reduce OFF-state current, and reduce short-channel effects (SCEs). One such multi-gate device is horizontal gate-all-around (HGAA) transistor, whose gate structure extends around its horizontal channel region providing access to the channel region on all sides. The HGAA transistors are compatible with conventional complementary metal-oxide-semiconductor (CMOS) processes, allowing them to be aggressively scaled down while maintaining gate control and mitigating SCEs. However, fabrication of the HGAA transistors can be challenging. For example, channel formation by epitaxially growing stacked semiconductor materials for HGAA transistors by the current methods is not satisfactory in all respects, especially when the device pitch is small, such as 40 nanometers (nm) or smaller.